Q: Is it possible to have a rabbi present at the Catholic wedding ceremony and to have them do some sort of blessing or prayer outside the ceremony? This I believe is what a couple I have is hoping to do. Thank you for your help.
A: My opinion is yes, a rabbi may take part—even during the ceremony.
Here’s a quote from the Vatican’s ecumenical directory: “158. Upon request of the couple, the local Ordinary may permit the Catholic priest to invite the minister of the party of the other Church or ecclesial Community to participate in the celebration of the marriage, to read from the Scriptures, give a brief exhortation and bless the couple.”
That covers the circumstance of a Catholic marrying a Christian. I don’t know of a similar Vatican permission pertaining to the Catholic who marries an unbaptized person, but I think the principle should apply.
A rabbi may read from the Scriptures, give a brief exhortation, and/or bless the couple. During the ceremony.